1. Field of the Invention
The present invention relates to a hydraulically actuated wheel end assembly, and more particularly to a wheel end assembly including a friction clutch for selectively and independently controlling distribution of an engine torque between laterally opposed vehicle wheels for eliminating the necessity for a differential assembly.
2. Description of the Prior Art
Drive train system of current four-wheel drive vehicles conventionally include a front differential gearing adapted to distribute a driving force between left and right front wheels, a center differential gearing adapted to distribute the driving force between the front wheels and rear wheels, and a rear differential gearing adapted to distribute the driving force between the left and right rear wheels. Also, the four-wheel drive vehicles usually include a clutch for intermittently transmitting the driving force to a transfer means adapted to transmit the driving force for the front wheels to the rear wheels.
To transmit the driving force to the left and right rear wheels, for example, when the vehicle runs out of a muddy place, a full-time type four-wheel drive vehicle is accompanied by a problem that it is necessary to mount a differential lock device on the center differential and the rear differential, resulting in an undesirabe increase in the number of parts and a complicated structure. A part-time type four-wheel drive vehicle is accompanied by a problem that because clutches are provided on the transfer means, the number of parts is increased, and the structure is complicated. Moreover, since driving torque is equally transmitted to both wheels by the differential gearing, it is extremely complicated to improve stability and driveability at cornering of such drive train system.
The present invention provides a novel vehicular axle assembly, especially for a four-wheel drive motor vehicle.
The vehicular axle assembly in accordance with the preferred embodiment of the present invention includes an input shaft, a drive gear assembly connecting the input shaft to a pair of output shafts, a wheel end disconnect assembly disposed between and selectively connecting each of the pair of the output shafts to a corresponding one of said wheel ends, each of the wheel end disconnect assemblies has a hydraulically actuated friction clutch assembly integrated with the corresponding one of the wheel ends for facilitating both selective torque coupling and limited slip between either said wheel ends and the corresponding output shafts, and a control system controlling the friction clutch assemblies to selectively transfer torque from the input shaft to either the wheel ends.
In accordance with the first exemplary embodiment of the present invention, the axle assembly of the present invention is employed in one of the axles of the four-wheel drive motor vehicle, such as a rear axle. The invention further includes an electronic control system providing an active control of the driving torque distribution between the left and right rear wheels of the rear axle assembly. The electronic control system includes an electronic control unit (ECU), and a hydraulic actuator adapted to supply pressurized hydraulic fluid to conventional wheel brake assemblies and the hydraulically actuated friction clutch assemblies integrated with the wheel ends of the rear axle. An independent sensor arrays or vehicle Controller Area Network (CAN) Bus is provided to generate input signals to the ECU. The ECU controls both the braking system (including an Antilock Braking System (ABS)), and the driving torque distribution between the left and right rear wheels of the rear axle assembly.
In accordance with the second exemplary embodiment of the present invention, the axle assembly of the present invention is employed in both front and rear axles of the four-wheel drive vehicle.
Therefore, the vehicular axle assembly in accordance with the present invention represents a novel arrangement that allows selective and independent control of a driving torque distribution between the laterally opposed vehicle wheels for improving stability and drivability at cornering and on slippery road surfaces, and eliminates an axle differential gearing.